Spatio-temporal trends of seasonal climate parameters in the Western Himalayan Region

Climate change represents a significant global challenge, affecting rainfall and temperature patterns worldwide. The study analyzed climatic trends in two contrasting districts in Indian Himalayan Region viz., Solan district of Himachal Pradesh covering the foothill to mid-hills of Himalayas, and Tehri Garhwal district of Uttarakhand encompassing foothills to the Greater Himalayas. Temperature, precipitation, and soil moisture trends were analyzed using long-term (1964 to 1993 and 1994 to 2023) TerraClimate seasonal raster datasets and nonparametric statistical methods, i.e., the Mann-Kendall test and Sen's slope estimator. During the pre-urbanization period (1964-1993), Tehri Garhwal had increasing winter precipitation (1.71 to 4.93 mm year⁻¹) and soil moisture (0.45 to 1.45 mm year⁻¹), although a strong decline in monsoon precipitation (- 13.79 to - 2.00 mm year⁻¹) with decreasing soil moisture (- 0.15 to 0.07 mm year⁻¹) and weak temperature trends. In contrast, Solan experienced increasing winter (1.57 to 2.61 mm year⁻¹) and summer precipitation (0.50 to 1.13 mm year⁻¹) and soil moisture (0.51 to 1.42 mm year⁻¹ in winter; 0.65 to 1.09 in summer), while monsoon (- 0.29 to - 0.47 mm year⁻¹) and post-monsoon precipitation declined (- 0.55 to - 0.07 mm year⁻¹). During the post-urbanization period (1994-2023), Tehri Garhwal had high spatial variability in monsoon precipitation (- 5.19 to 6.79 mm year⁻¹), although Solan experienced a consistent monsoon decline (- 1.78 to - 2.76 mm year⁻¹). Winter maximum temperature increased by 0.017-0.034 °C year⁻¹ in Tehri Garhwal and 0.024-0.035 °C year⁻¹ in Solan. Minimum temperature trends were higher in Solan, particularly during the post-monsoon season (0.044-0.062 °C year⁻¹). Tehri Garhwal had declining soil moisture during winter and summer (- 0.82 mm year⁻¹) and Solan had near-stable to slightly positive post-monsoon soil moisture trends (- 0.004 to 0.082). The study underscores the urgent need for localized climate adaptation measures to ensure the sustainability of water and land resources under climate change.